Embodiments presented herein relate generally to computerized tomography (CT) systems, and more particularly to systems and methods for processing sinograms obtained in CT systems.
CT or computerized axial tomography (CAT) is a medical imaging technique employing tomography generated by computer processing. CT imaging provides cross-sectional images or “slices” of anatomy. CT systems produce images using X-rays, based on the ability of various anatomical structures to block or absorb X-rays.
Conventional CT imaging systems comprise a motorized patient bed to advance the patient into a circular patient bore in the CT imaging system. As the patient passes through the CT imaging system, an X-ray emitter rotates around the inside of the patient bore. The X-ray emitter emits a narrow, cone-shaped beam of X-rays to irradiate a section of the patient's body. X-ray detectors on the opposite side of the X-ray emitter record the X-rays exiting the patient's body, thus forming an X-ray view at one angle of the X-ray emitter. Multiple such views are collected to produce a complete CT sinogram.
Once the sinogram data has been acquired, an image processor reconstructs the individual views into a cross-sectional slice of internal organs and tissues within the anatomical structure. Typically, the sinogram data of the individual slices is integrated to generate a three dimensional volumetric information (3D-CT scan). Such a 3D-CT scan is viewable from multiple different perspectives.
Accurate CT reconstruction is difficult due to a number of reasons. For example, in cone beam CT some sections of the patient's body are sometimes inside and sometimes outside the emitted X-ray beam, resulting in truncation of the projection at the edges. Such truncation is known as z-truncation. Z-truncation results in deterioration in image quality at the edges of reconstructed volume, and generates undesired artifacts. To mitigate artifacts generated due to z-truncation, data extrapolation techniques are required. One known technique of extrapolation estimates the truncated data by simple duplication extrapolation. In other words, the duplication extrapolation technique copies the first or last row of the available scan data to synthesize extra projection rows. However, such a technique may introduce inconsistencies between different views of the scan data and may result in false anatomic structures or streaks in the reconstructed images.
Therefore, there is a need for a system and a method that overcomes these and other disadvantages associated with known CT reconstruction techniques.